-25% is the change from 680 to 510
Calculation steps:
[( 510 - 680 ) ÷ 680] x 100 = -25%
Formula
Percentage change = [(510 - 680) / 680] x 100
Subtract the new number by the original number
510 - 680 = -170
-170 ÷ 680 = -0.25
-0.25 x 100 = -25%
Example